The present invention relates to a process for preparing a deodorized alkyl ether sulfate aqueous concentrate which comprises treating a high-concentration alkyl ether sulfate aqueous solution under reduced pressure to thereby achieve its deodorization and concentration simultaneously.
As a means for obtaining a high concentration alkyl ether sulfate aqueous solution there is known for instance a process which comprises concentration a low concentrated alkyl ether sulfate aqueous solution by means of a rotary thin film type evaporator as disclosed in Japanese Published Examined Patent Application No. 29304/1978, and a process for obtaining a high concentration alkyl ether sulfate aqueous solution by mixing an excess of alkali-containing alky ether sulfate with a non-neutralizer as disclosed in Japanese Published Unexamined Patent Application No. 64564/1980.
Alkyl ether sulfate contains odorous components such as alcohol, which is itself odorous, cyclic ether which is by-produced in a small quantity during the sulfation reaction and the like. U.S. Pat. No. 3,893,940 discloses a process for removing unreacted oils from the sulfonates or sulfates of olefins having 12 to 22 carbon atoms, paraffins having 12 to 22 carbon atoms and aliphatic monohydric alcohols having 8 to 22 carbon atoms, adding polyhydric alcohol, alcohol ethoxylate or the like to the starting material and treating the resulting mixture at reduced pressure. The concentration of the starting sulfate or sulfonate in this instance, however, is not high, such as 27% or so.
As a matter of course, it is true in the case of an alkyl ether sulfate aqueous solution that the more concentrated the solution the more profitable it is from the viewpoint of far wider application, transportation or storage. However, it is noted in the preparation of alkyl ether sulfate that with the increase of its concentration, the quantities of hydrolysis product of alkyl ether sulfate, cyclic ether and the like also increase. And, in the case of an alkyl ether sulfate aqueous solution, its viscosity also increases rapidly with the increase of its concentration. Due to this, it has been considered difficult to remove said odorous components efficiently under high concentration conditions, and thus the means for deodorization has not been pursued up to now as the subject of investigation.